Comorbidities and RA – study findings

Interview and article by Christine Clark

A recent Canadian study examining comorbidities before and after the diagnosis of rheumatoid arthritis (RA) produced a number of interesting findings, Dr Mark Tatangelo, the lead researcher explains.

This study showed that there were differences in the patterns of comorbidities in the RA and control groups. One key finding was that RA-associated comorbidities were evident months or years before the diagnosis of RA was made.

“We were surprised to see how early the observable differences between RA patients and non-RA patients occurred. That was definitely an interesting finding for our team”, says Dr Tatangelo

Another feature of interest was the decrease in comorbidities after diagnosis that suggested a possible effect of treatment and improvements as a result of treatment.

The results show a sharp rise in comorbidities at the time of diagnosis and a sharp fall immediately afterwards and this is partly due to the accrual method. “Because it is an administrative study you need to have interactions with the health care system to be identified as RA, but even controlling for those identification increases we can see that RA patients’ healthcare utilisation becomes more intense at the time of diagnosis – again likely due to an increase in unexplained symptoms and patients seeking a diagnosis for their disease”, says Dr Tatangelo. The sharp fall in comorbidities immediately after diagnosis wards probably reflects the effects of treatment and a reduction of healthcare resource use, he notes.  

A number of improvements in the treatment of RA have occurred during the period in question, including the use of aggressive treatment strategies, the use of triple disease-modifying anti-rheumatic drug (DMARD) therapy and the introduction of biologics and janus kinase (JAK) inhibitors. All of these could have contributed to the observed decrease in comorbidities after diagnosis.  However, the impact of biologic therapies was of particular interest and one way to look at this was to stratify the results by the year of diagnosis. Dr Tatangelo explains, “We did note in our study window the substantial increase in the use of biologics, because zero patients had biologics before 2001 but by 2015 we had at least 30,000 estimated users in our cohort – so it is certainly one of the explanations for a decrease in comorbidities over calendar time.

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